How to express Strings in Swift using Unicode hexadecimal values (UTF-16)

I want to write a Unicode string using hexadecimal values in Swift. I have read the documentation for String and Character so I know that I can use special Unicode characters directly in strings like the following:

Character

where n is a hexadecimal number up to 8 digits long. The valid range for a Unicode scalar is U+0 to U+D7FF and U+E000 to U+10FFFF inclusive. (The U+D800 to U+DFFF range is for surrogate pairs, which are not scalars themselves, but are used in UTF-16 for encoding the higher value scalars.)